1. Field of the Invention
The present invention relates to a control apparatus of a vehicle, and particularly, to a technique for controlling an internal combustion engine of a vehicle when adjusting an amount of hydraulic fluid of an automatic transmission in the vehicle incorporating the automatic transmission.
2. Description of the Background Art
Among automobiles, particularly many passenger cars employ an automatic transmission (AT) as a transmission. The automatic transmission is constituted by a torque converter and a transmission mechanism (irrespective of whether it is a stepped transmission using gears or the like or a continuously variable transmission using a belt of the like), wherein the torque converter and the transmission mechanism are filled with a hydraulic fluid (oil). If the amount of oil is less than a determined amount, an oil pump may not be able to intake the oil and may intake air instead when cornering or when going up a hill at a low temperature, whereby the driving force may be reduced.
On the other hand, with an excessive amount of oil, if the oil level is raised by expansion when, for example, the oil is at a high temperature, the oil is agitated by a rotary member such as a clutch drum of a gear type transmission mechanism. This increases the mechanical loss and further raises the oil temperature. Thus, the durability of the automatic transmission may be deteriorated and oil blow out from a breather may be incurred. Accordingly, the amount of oil must be constantly maintained properly.
Since the oil of an automatic transmission has its viscosity changed in accordance with its temperature, and the oil level changes by expansion, the adjustment to a proper amount should preferably be performed fixing the oil temperature condition. Normally, the oil is often managed at the level corresponding to 158-176° F., which is a temperature range that can be attained by a general driving of a vehicle and in which the circulation of oil is easier to be stabilized. It is difficult to increase the oil temperature to such degrees at an automobile manufacturing factory in relation to the number of steps, and therefore a check level is separately set for management that corresponds to an oil temperature obtained by measurement after an inspection step.
Thus, although it requires some steps, the oil level can thoroughly be managed at a manufacturing factory. However, as the oil deteriorates with age, an oil change is also done at a dealer when the vehicle is used over a long period. In this case, as means for precisely obtaining the oil temperature is not available, the automobile is actually driven and the internal temperature of the transmission is waited for to rise, and then the oil level is managed.
An actual method therefor is performed by driving the vehicle under a prescribed condition, for example for 30 minutes at 38 mile per hour, and thereafter checking the amount of oil. Driving the vehicle under this condition, the internal temperature of the transmission is stabilized to about 158-176° F. Thus, the oil can be supplied under the condition of an actual usage. However, such a method requires a course for driving the vehicle, as well as many steps.
Japanese Patent Laying-Open No. 11-325235 discloses an oil level detection and display method for an automatic transmission, for easily supplying a proper amount of oil when supplying the oil to an automobile incorporating such an automatic transmission. The oil level detection and display method for an automatic transmission is a method, in an automobile incorporating a failure diagnosis system in an AT controller, for causing the AT controller to generate a display output indicative of oil level detection conditions of an automatic transmission are all satisfied, wherein, as the oil level detection conditions of an automatic transmission, at least an engine is running at an idling speed, the vehicle is parking, and a speed change selection lever is in N range or P range position.
According to the oil level detection and display method for an automatic transmission, when short-circuiting a diagnosis terminal of the AT controller, different display is presented between when it is appropriate to detect the oil level of the automatic transmission and when it is not. In this case, if the engine is running at the idling speed and the vehicle is parking, then the oil is distributed over the necessary portions and stabilized. Thus, the oil can also be supplied in a proper amount when an oil change is done at a dealer or the like where a course for actually driving the vehicle is not available.
However, the oil level detection conditions in the oil level detection and display method for an automatic transmission disclosed in Japanese Patent Laying-Open No. 11-325235 only require that an engine is running at an idling speed, that the vehicle is parking, and that a speed change selection lever is in N range or P range position. The engine speed may not be constant even when idling, depending on the effect of auxiliary equipment actuated by revolution of the engine. If the engine speed changes in such a state, an amount of oil sticking inside (when the hydraulic fluid is low in temperature and high in viscosity, it sticks to a housing or the like in the transmission mechanism and would not return to an oil pan) and/or a hydraulic fluid temperature do not attain desirable values. Accordingly, the oil level fluctuates and precise adjustment of the oil level is difficult.